capo-hardening?

[Mark Cramer]

Okay, I've been to the archives and had a look.

To provide background, I can tell you that this capo was dressed upon
re-stringing. Though, as I had personally done neither, and the noise was
bad, I removed the string and re-surfaced the capo again, this time to a
smaller radius.

If you've travelled this path before you will know the results were
superb,... but very short-lived. :>(

In reading an article, and in consultation with Paul Dempsey, I then made
some brass shims to raise the front-duplex angle. No luck.

BTW, this seems similar to the approach Ron N. advocates in the CAUT digest;
3/1/99.

In contrast, Ron Overs, who is also mentioned in that thread, advocates
"lowering" the string deflection angle (to 15 degrees, I believe) rather
than raising it. He does deliberately shorten the duplex length though, and
hardens both capo and diplex bars as well.

As the zinging in this piano cannot be eliminated with front duplex muting,
the zings re-appeared in the duration of one tuning, and the grooves along
with them, I've decided that the capoo hardness must be the villian.

Now what to do?

In reading Roger's post regarding quenching the heated bar via the (moist)
sand of the foundry, I'm wondering, with the help of my very skilled welder,
if an "in-the-piano" procedure may be possible.

Surely with all the "dare-devils" on this list, someone must've,.... anyone?

Mark C.


-----Original Message-----
From: owner-caut@ptg.org [mailto:owner-caut@ptg.org]On Behalf Of jolly
roger
Sent: Saturday, September 22, 2001 12:16 AM
To: caut@ptg.org
Subject: Re: capo-hardening?



>Based on Roger's post, I'm guessing the key is the skill of the welder, not
>just the type of welding device used.
>
My metallurgy knowledge is non-existent, but I wonder about the hardness of
>cast iron at the v-bar from normal surface cooling at the time of
>manufacture, vs. torch-hardening and/or TIG reflowing.
>
>Bill Shull

Hi Bill,
            Yes there is a high level of skill happening here, It is done
so there is barely any discoloration of the finish, and the result is just
case hardening of the surface area.

In a sand cast pour, the water in the sand acts to quench the surface, and
case harden  the surface.  If too much shaping and filing takes place at
the piano factory, the hardened surface may be completely removed. Just one
of the reasons that a new piano may exhibit excessive V noise right off the
bat.   The mere act of stringing starts to form a significant groove in the
soft cast iron.

In the foundry, if the sand box is too dry,  hardly any case hardening
takes place, due to the absence of water.

Roger